Reading one of Connie Willis’ time travel novels is like watching a master paper-folder perform a particularly difficult feat of origami. It seems simple at first, but then there are a few folds and twists, edges are forced together and bent apart, there’s a few points where you can’t even see exactly what her hands are doing, but when she’s finished, you have the pleasure of seeing something intricate and beautiful come into being right before your eyes.

The basic premise of her time travel works is pretty simple: in the future, we have time travel (but not cell phones, as you may recall from The Doomsday Book). The exact means by which it works is not revealed to us, which makes sense – the books aren’t about the mechanics of time travel but rather the results. On the other hand, the rules of time travel are vividly clear:

You can only go to the past.

You can’t bring back any souvenirs.

You can’t change anything.

No, you can’t bring back cathedrals either.

That last part is really important, and it is held as gospel by the historians who use the mechanism to go visit various eras in history. The space-time continuum will do its damnedest to keep a traveler from altering the natural flow of events. For example, in order to even get the machine to work, you have to be able to blend in – that means proper clothes and appearance, no hidden wristwatches or things like that. If you’re carrying a disease that the locals might not be prepared for, if you don’t know the language – hell, maybe if you’re just the wrong skin color, the system won’t open up and let you through.

Once you’re ready to go and fit in, there’s still the matter of being able to change events. Now it is true that simply by existing you have already changed things. You move air molecules that were moved differently before. You’re pouring heat into the environment that wasn’t there before. You’re making contact with the surfaces around you, shedding skin cells, making noises – and that’s before you even meet anyone. Once you’re out on the street (or country lane or agora or whatever), you’re interacting with people no matter what you do. They see you, you register in their consciousness to one degree or another – you’re changing things just by your very existence.

The continuum, it seems, is only concerned about big changes. You can’t get anywhere near Hitler, for example, or Kennedy on the day of his assassination. No matter how hard you try or how precisely you set the controls, you will end up displaced either in time or in space or both, unable to do a damned thing. The continuum protects itself, and historians can be assured that their actions in the past have no real consequence.

Or do they?

Dangerous? Nonsense. Now out of my way, I’ve milk to deliver.

Three British historians have gone back in time to one of the most dramatic and dangerous eras in recent history – the Blitz of World War 2. This was a period of about eight months between 1940 and 1941 when German bombers tried to reduce England to a smoking pile of rubble. They dropped a hundred tons of bombs, cause immeasurable property damage, and killed thousands of people. Life in this time was dangerous, terrifying, and uncertain, and anyone who lived through it was aware that they could die on any one of the raids.

Despite this, the English showed a solidarity and a steadfastness that won the respect of the world (or at least the parts of the world that weren’t trying to bomb it). Everyone – soldiers and civilians – were encouraged to do their part during the war, and every action you took had to be considered in the greater scheme of keeping people safe and keeping London alive. A popular sentiment about the time is that there really were no civilians. Everyone played a hand in getting England through the Blitz, from the Prime Minister to the milkman. If you were an historian looking to see how ordinary people coped in extraordinary times, the Blitz would be the perfect scenario to observe.

Polly Sebastian is in the thick of it. She has traveled to London, September 1940, with the intention of getting a job in a department store in the middle of town. She arrives during a bombing raid and is ushered into a shelter full of people who will change her life.

Mike Davis wanted to see some true citizen-heroes, so he posed as an American reporter in order to witness the Dunkirk Rescue in May of 1940. He ends up far from Dunkirk, however, and his efforts to get there end up in him becoming part of the action.

“Oy dinn’t do nuffin'”

Eileen O’Reilly has gone to witness the children’s evacuation of 1939-1940. She poses as a maid in a manor house in the country, there to watch over children who had been sent from London to keep them safe from the war. Eileen has to not only contend with dozens of city children, an outbreak of the measles, and learning to drive an ancient Bentley, but she also has two of the most terrible children in England under her care – Alf and Binnie Hodbin.

All of these assignments would be a major task for any historian, but these three soon discover that they are not in an ordinary situation. It becomes clear to them that their actions are having consequences – Mike saves a soldier who in turn helps hundreds more. Polly says a few words that changes a young woman’s life. Eileen gives medicine to a young girl that no one living at that time would have given, thus keeping her alive. The unbreakable rule about historians not being able to affect the continuum seems to be bending.

What’s worse, none of them are able to access their “drop points” to return to 2060. They’re stuck in a strange and dangerous time, and are now just as at risk as any contemporary person is.

This was originally meant to be only one book – All Clear – but it kept growing and expanding so much that Willis split it into two volumes. This allowed her to not only show off what must have been an immeasurable amount of research over the eight years it took to write the novels, but gave us more time to become immersed and invested in a story that is both funny and heart-wrenching in turns. Our time-travelers are in very real danger, of more than one sort, and you really do feel their desperation and hope for their success.

There, there now. Train tracks are much safer than what’s going on up there.

It would be so hard to sum up this book, except to say that it reminds us that everything – and everyone – is significant. The fate of the future rests on the backs of not only generals and prime ministers, but on shopkeepers and children. Words can change the world just as much as bombs, and every action you take contributes to the vast, infinitely complex unfolding of history. As our characters learn, there is no such thing as a passive observer. We are all part of the history, the society, and the world around us, whether we like it or not.

We may not know how it’s all going to unfold in the end, for good or ill, and that’s unfortunate. So all we can do when faced with an uncertain future is what the British did when oblivion came flying over the Channel to their shores. Stand firm and do your bit, and let history take care of itself.